As power devices having a high withstand voltage (600 V or higher), semiconductor devices having an IGBT are used. In such a semiconductor device, a termination region is arranged around an active region in which the IGBT is provided.
Unlike a CMOS (complementary metal oxide semiconductor) transistor or the like used for an LSI (large scale integration), the IGBT which is a power semiconductor is required to be furnished with a breakdown capability such as a current breaking capability during turn-off operation in addition to a reduction of on-voltage, speed enhancement and improvement of current drive capability. Here, the current breaking capability refers to a maximum current density interruptible by the semiconductor device without causing destruction at the time of turn-off.
A semiconductor device is proposed, in which no P type collector layer exists in a termination region and an N type buffer layer is directly connected to a collector electrode (e.g., see FIG. 1 of Patent Literature 1). This makes it possible to lower carrier concentration during turn-off operation, facilitate depletion and thereby reduce electric field strength. In this way, it is possible to improve a current breaking capability during the turn-off operation.